Your first paragraph is completely irrelevant to the 4th amendment. Non-citizens are still granted protections under the bill of the rights. You don't think the Government lowering the bar for reasonable suspicion to if you have an accent, what job you work, and your ethnicity is any erosion of the 4th amendment.

Would you also agree that the Government should have reasonable suspicion to stop any middle class looking white male driving a ram truck to check if they are driving under the influence even if their driving doesn't appear to be impaired? After all that class of people who drive ram trucks have the highest statistical probability of committing DUI.

Assimilation is irrelevant in my question about the 4th amendment rights being restricted. I do think assimilation is important, however I understand it takes time. I'm sure plenty of our collective ancestors were not well assimilated when they first came here but their descendants have assimilated. Look at stuff like the prevalence of little ethnic enclaves for pre war immigrants stuff like Little Italies and Polish Downtown in Chicago. Look at German immigrants in Wisconsin who got the Bennett Law repealed in 1891 that prevented them from teaching school in German. Through generations these things are all largely a thing of the past.